Integrated audio amplifier

Abstract

An audio amplifier having an amplifier section and a power supply. The power supply comprises a positive power supply section and a negative power supply section, each of which provides voltage to the positive and negative power inputs to the amplifier. The control circuitry for the power supply sections causes the voltage output from the power supply sections to vary in accordance with the amplitude of the audio signal so that the power supply voltages track the positive and negative components of the audio signal so that the supply voltages are at a predetermined level above and below the positive and negative components of the audio signal, respectively. Each of the power supply sections has a pair of switches which open and close alternately to transmit power pulses to opposite ends of the primary winding, and the secondary winding in turn transmit power pulses alternately through a filter component to its respective input of the amplifier section.

I claim: 
     
       1. An audio amplifier comprising: a) a power amplifier section which receives an audio input signal and positive and negative voltage power inputs to produce an audio output;   b) a power supply comprising a positive power supply section and a negative power supply section;   c) said positive power supply section comprising; i. a first transformer having a primary and a secondary winding, with the secondary winding being operatively connected to said power amplifier section to supply positive voltage power input to the power amplifier section;   ii. a first power switching portion to supply current pulses to the primary winding;   iii. a first filter circuit component connected to an output of said secondary winding of the first transformer to maintain the voltage of the positive power output as a continuing variable voltage input;     d) said negative power supply section comprising: i. a second transformer having a primary and a secondary winding, with the secondary winding being operatively connected to said power amplifier section to supply negative voltage power input to the power amplifier section;   ii. a second power switching portion to supply current pulses to the primary winding;   iii. a second filter circuit component connected to an output of said secondary winding of the second transformer to maintain the voltage of the negative power output as a continuing variable voltage input;     e) a control circuit responsive to an audio input signal to transmit pulse control signals to the first and second switching portions to cause said first and second switching portions to open and close in a manner to transmit current pulses to the primary windings of the first and second transformers, with power of the pulses having a proportional relationship to the strength of the audio signal, so that the positive and negative voltage power inputs to the amplifier section tracks the audio signal in a manner to maintain the positive and negative voltage power inputs at a predetermined level range above and below voltage of the audio input.   
     
     
       2. The amplifier as recited in claim 1, wherein the switching portion for each of said positive and negative supply sections comprises two switches, connected to opposite sides of the primary winding of the related transformer, so that the pulses of one of said switches passes through the related primary winding of one direction, while the pulses of the other switch pass through the related primary winding in an opposite direction. 
     
     
       3. The amplifier as recited in claim 2, wherein an intermediate portion of each of said primary windings is connected to a power source. 
     
     
       4. The amplifier as recited in claim 3, wherein the secondary winding of each transformer is connected to ground at an intermediate location of each secondary winding. 
     
     
       5. The amplifier as recited in claim 2, wherein the secondary winding of each transformer is connected to ground at an intermediate location of each secondary winding. 
     
     
       6. The amplifier as recited in claim 1, wherein the control circuit comprises a pulse width modulator which receives a clock input to initiate successive pulse signals, and having an audio signal input to cause said pulse width modulator to transmit pulse signals having a pulse strength with a proportional relationship to said audio signal. 
     
     
       7. The amplifier as recited in claim 6, wherein each pulse width modulator creates square wave signal pulses, with the width of the pulses varying in accordance with the amplitude of the audio signal. 
     
     
       8. The amplifier as recited in claim 6, wherein the switching portion for each of said positive and negative supply sections comprises two switches, connected to opposite sides of the related primary winding of the transformer, so that the pulses of one of said switches passes through the related primary winding in one direction, while the pulses of the other switch pass through the related primary winding in an opposite direction, said control circuit comprises a pulse width modulator which receives a clock input to initiate successive pulse signals, and having an audio signal input to cause said pulse width modulator to transmit pulse signals having a pulse strength with a proportional relationship to said audio signal. 
     
     
       9. The amplifier as recited in claim 1, wherein each secondary winding has two end connections and first and second diodes to receive the output at each of said end connections with the output of the diodes being directed to the power amplifier section. 
     
     
       10. The amplifier as recited in claim 9, wherein the switching portion for each of said positive and negative supply sections comprises two switches, connected to opposite sides of the primary winding of the transformer, so that the pulses of one of said switches passes through the primary winding in one direction, while the pulses of the other switch pass through the primary winding in an opposite direction, said control circuit closes the first and second switches of each of said supply power sections alternately, so that current pulses from said secondary winding are transmitted alternately through said first and second diodes. 
     
     
       11. The amplifier as recited in claim 9, wherein each of the filter components of the two power supply sections comprises an induction coil to receive the output of the secondary, and a capacitor connected at a location between the induction coil and the amplifier section. 
     
     
       12. The amplifier as recited in claim 1, wherein each of the filter circuit components of the two power supply sections comprises an induction coil to receive the output of the secondary, and a capacitor connected at a location between the induction coil and the amplifier section. 
     
     
       13. A method of amplifying an audio signal, comprising: a. providing a power amplifier section having an audio input signal port and positive and negative voltage power input ports;   b. providing a power supply comprising a positive power supply section and a negative power supply section where said positive power supply section comprises: i. a first transformer having a primary and a secondary winding, with the secondary winding being operatively connected to said power amplifier section;   ii. a first power switching means operatively connected to the primary winding;   iii. a first filter circuit component connected to an output of said secondary winding of the first transformer;   and wherein said negative supply power section comprises:   i. a second transformer having a primary and a secondary winding, with the secondary winding being operatively connected to said power amplifier section to supply negative voltage power input to the power amplifier section;   ii. a second power switch means to supply current pulses to the primary winding;   iii. a second filter circuit component connected to an output of said secondary winding of the second transformer to maintain the voltage of the negative power output as a continuing variable voltage input;     c. transmitting pulse control signals to the first and second switching portions to cause the first and second switching portions to open and close in a manner to transmit current pulses to the primary winding of the first and second transformers, with power of the pulses having a proportional relationship to the strength of the audio signal, so that the positive and negative voltage power inputs to the amplifier section track the audio signal in a manner to maintain the positive and negative input voltages at a predetermined level range above and below, respectively, the voltage of the audio input.   
     
     
       14. The method as recited in claim 13, wherein the switching portion for each of said positive and negative supply sections comprises two switches, connected to opposite sides of the primary winding of the related transformer, said method comprising transmitting pulses of one of said switches passes through the related primary winding in one direction, and the pulses of the other switch through the related primary winding in an opposite direction. 
     
     
       15. The method as recited in claim 14, wherein an intermediate portion of each of said primary windings is connected to a power source. 
     
     
       16. The method as recited in claim 15, wherein the secondary winding of each transformer is connected to ground at an intermediate location of each secondary winding. 
     
     
       17. The method as recited in claim 13, wherein said pulse control signals are generated by a pulse width modulator which receives a clock input to initiate successive pulse signals, and providing an audio signal input to cause said pulse width modulator to transmit pulse signals having a pulse strength with a proportional relationship to said audio signal, and the pulse width modulator creates square wave signal pulses, with the width of the pulses varying in accordance with the amplitude of the audio signal. 
     
     
       18. The method as recited in claim 13, wherein each secondary winding has two end connections and first and second diodes to receive the output at each of said end connections with the output of the diodes being directed to the power amplifier section. 
     
     
       19. The method as recited in claim 18, wherein the switching portion for each of said positive and negative supply sections comprises two switches, connected to opposite sides of the primary winding of the transformer, so that the pulses of one of said switches passes through the primary winding in one direction, while the pulses of the other switch pass through the primary winding in an opposite direction, each control circuit closes the first and second switches of each of said supply power sections alternately, so that current pulses from said secondary winding are transmitted alternately through said first and second diodes. 
     
     
       20. The method as recited in claim 19, wherein each of the filter components of the two power supply sections comprises an induction coil to receive the output of the secondary, and a capacitor connected at a location between the induction coil and the amplifier section.